July will roar in Friday with high temperatures and unhealthy ozone levels, prompting warnings that Mainers take precautions to stay safe and avoid the air pollution.

Winds from the south are expected to push ground-level ozone concentrations to unhealthy levels along the coast, posing a significant threat to people with breathing challenges from Kittery to Acadia National Park, according to the Maine Department of Environmental Protection.

Temperatures will hit the mid-80s along the coast and low 90s inland, but humidity will be moderate, with dew points in the 50s and 60s, said Jerry Combs, a meteorologist with the National Weather Service in Gray.

“Friday is going to be hot,” Combs said. “Strong south-southwest winds are going to move in ahead of a cold front that will bring rainstorms into the region Friday night into Saturday.”

Ozone levels also will be high Friday in the hills and mountain regions, and moderate but noticeable inland for sensitive individuals, according to the MDEP’s air quality forecast website.

Higher ozone levels aren’t expected to continue beyond Friday, said Martha Webster, air quality meteorologist with the MDEP.


Ground-level ozone is a form of air pollution composed of three oxygen atoms. It is created when pollutants emitted by cars, power plants, industrial boilers, refineries, chemical plants and other sources are exposed to sunlight, according to the U.S. Environmental Protection Agency.

Ozone is most likely to reach unhealthy levels on hot sunny days in urban environments, but it can happen during colder months and be transported long distances to rural areas by wind, as is the case in Maine.

High ozone levels can cause reduced lung function and irritation for children, healthy adults who exert themselves, and individuals suffering from a respiratory disease such as asthma, bronchitis or chronic obstructive pulmonary disease.

Individuals may notice a shortness of breath, coughing, throat irritation or an uncomfortable sensation in their chest, the MDEP says.

To stay safe during periods of unhealthy air quality, experts recommend avoiding strenuous outdoor activity during the afternoon and staying in shady or air-conditioned locations if you’re at risk.

“If you’re going to be outside, stay hydrated, take breaks and find some shade,” Combs said.

The extended forecast shows temperatures in the low to mid-80s Sunday and upper 70s to low 80s Monday, with a slight chance of showers on the Fourth of July.

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